U.S. patent number 6,127,447 [Application Number 09/363,896] was granted by the patent office on 2000-10-03 for photopolymerization process and composition employing a charge transfer complex and cationic photoinitiator.
This patent grant is currently assigned to Fusion UV Systems, Inc.. Invention is credited to Mohamed R. Amin, Roger McCartney, Mark Mitry.
United States Patent |
6,127,447 |
Mitry , et al. |
October 3, 2000 |
Photopolymerization process and composition employing a charge
transfer complex and cationic photoinitiator
Abstract
A radiation curable coating composition is provided and includes
an effective amount of cationic photoinitiator, in combination with
a charge transfer complex, the charge transfer complex comprising
at least one electron withdrawing reactant component and at least
one electron donating reactant component free radically reactive
therewith, the electron withdrawing reactant component comprising
an unsaturated nitrogen containing compound and the electron
donating reactant component comprising an unsaturated compound
having at least one vinyl ether group, the electron donating
reactant component may be separate from or structurally
incorporated within the electron withdrawing reactant component and
an effective amount of a cationic photoinitiator. A
photopolymerization process employing the composition is also
provided.
Inventors: |
Mitry; Mark (Woodbury, MN),
McCartney; Roger (St. Louis, MO), Amin; Mohamed R.
(Gaithersburg, MD) |
Assignee: |
Fusion UV Systems, Inc.
(Gaithersburg, MD)
|
Family
ID: |
22246904 |
Appl.
No.: |
09/363,896 |
Filed: |
July 30, 1999 |
Current U.S.
Class: |
522/107; 427/517;
522/168; 522/913; 522/188; 522/186; 522/180; 522/178; 522/167;
427/520; 522/104 |
Current CPC
Class: |
C09D
4/06 (20130101); C08F 2/50 (20130101); C09D
167/06 (20130101); G03F 7/027 (20130101); G03F
7/038 (20130101); C09D 4/06 (20130101); C08F
283/01 (20130101); Y10S 522/913 (20130101) |
Current International
Class: |
C08F
2/46 (20060101); C08F 2/50 (20060101); G03F
7/027 (20060101); G03F 7/038 (20060101); C08F
002/46 (); C08F 002/48 (); C08F 216/12 (); C08F
222/06 () |
Field of
Search: |
;522/104,107,167,168,173,174,178,181,184,913,186,188 ;430/58
;427/517,520 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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|
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|
|
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|
947701 |
|
Jan 1964 |
|
GB |
|
WO 97/31981 |
|
Sep 1997 |
|
WO |
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WO 98/11151 |
|
Mar 1998 |
|
WO |
|
WO 98/11152 |
|
Mar 1998 |
|
WO |
|
Primary Examiner: Sergent; Rabon
Assistant Examiner: McClendon; Sanza L.
Attorney, Agent or Firm: Shlesinger Arkwright & Garvey
LLP
Parent Case Text
CROSS-REFERENCE TO RELATED APPLICATIONS
This application is a nonprovisional of provisional application
U.S. Ser. No. 60/094,742 filed on Jul. 31, 1998.
Claims
We claim:
1. A radiation curable coating composition comprising:
a) a charge transfer complex, said charge transfer complex
comprising at least one electron withdrawing reactant component and
at least one electron donating reactant component free radically
reactive therewith, said electron withdrawing reactant component
comprising an unsaturated nitrogen containing compound and said
electron donating reactant component comprising an unsaturated
compound having at least one vinyl ether group, said electron
donating reactant component at least one of separate from or
structurally incorporated within said at least one electron
withdrawing reactant component; and
b) an effective amount of a cationic photoinitiator.
2. A radiation curable coating composition as in claim 1 and
further comprising:
a) an effective amount of a free radical photoiniator.
3. A radiation curable coating composition as in claim 1 and
wherein:
a) said cationic photoinitiator comprises from about 1% by weight
to about 3% by weight of the total composition.
4. A radiation curable coating composition as in claim 2 and
wherein:
a) said free radical photoinitiator comprises from about 0.5% by
weight to about 1.0% by weight of the total composition.
5. A radiation curable coating composition as in claim 1 and
wherein:
a) said cationic photoinitiator is selected from the group
consisting of ionic cationic photoinitiators and nonionic cationic
photoinitiators.
6. A radiation curable coating composition as in claim 1 and
wherein:
a) said cationic photoinitiator is selected from the group
consisting of onium salts, organometallic salts, organosilanes,
latent sulphonic acids, triaryl sulphonium salts, ferrocenium
salts, sulphonyloxy ketones and silyl benzyl ethers.
7. A radiation curable coating composition as in claim 2 and
wherein:
a) said free radical photoinitiator is selected from the group
consisting of benzophenone, anthraquinone, thioxanthone, isobutyl
benzoin ether, alpha-diethoxyacetophenone and
alpha-dimethoxy-alpha-phenylacetothenone.
8. A radiation curable coating composition as in claim 1 and
wherein:
a) said unsaturated nitrogen containing compound and said
unsaturated compound having at least one vinyl ether group is a
compound selected from the group consisting of polyesters,
oligomers and monomers.
9. A radiation curable coating composition as in claim 8 and
wherein:
a) said unsaturated nitrogen containing compound ilo having at
least one
functional group selected from the group consisting of maleate,
fumarate, itaconate, citraconate and mesaconate groups.
10. A radiation curable coating composition as in claim 1 and
wherein:
a) said unsaturated nitrogen containing compound is a prepolymer
having a maleimid function.
11. A radiation curable coating composition as in claim 1 and
wherein:
a) said unsaturated nitrogen containing compound is a prepolyer
having a maleiate function.
12. A radiation curable coating composition as in claim 8 and
wherein:
a) said unsaturated compound having at least one vinyl ether group
is a non-polymerized, cocurable vinyl ether component free
radically reactive with the unsaturation of said unsaturated
polyester component.
13. A radiation curable coating composition as in claim 1 and
wherein:
a) said electron donating reactant component has ethylenic
unsaturation and an electron donating group greater than a vinyl
ether group.
14. A photopolymerization process comprising the steps of:
a) providing a radiation curable coating composition comprising a
charge transfer complex and effective amount of cationic
photoinitiator, the charge transfer complex comprising at least one
electron withdrawing reactant component and at least one electron
donating reactant component free radically reactive therewith, the
electron withdrawing reactant component comprising an unsaturated
nitrogen containing compound and the electron donating reactant
component comprising an unsaturated compound having at least one
vinyl ether group, the electron donating reactant component at
least one of separate from or structurally incorporated within the
at least one electron withdrawing reactant component;
b) applying the radiation curable coating composition to a
substrate to be coating; and
c) subjecting the applied radiation curable coating composition to
ultraviolet light for a period of time sufficient to polymerize the
charge transfer complex.
15. The polymerization process of claim 14 and wherein:
a) the applied ultraviolet light has a wavelength between about 180
to about 400 nanometers.
16. The polymerization process of claim 14 and wherein:
a) the dosage of the applied ultraviolet light is at least about
200 millejoules per square centimeter of the applied coating
surface area.
17. The polymerization process of claim 14 and wherein:
a) the coating composition further includes an effective amount of
a free radical photoiniator.
18. The polymerization process of claim 14 and wherein:
a) the cationic photoinitiator comprises from about 1% by weight to
about 3% by weight of the total free radical photoinitiator
composition.
19. The polymerization process of claim 15 and wherein:
a) the free radical photoinitiator comprises from about 0.5i by
weight to about 1.0% by weight of the total composition.
20. The polymerization process of claim 14 and wherein:
a) said cationic photoinitiator is selected from the group
consisting of ionic cationic photoinitiators and nonionic cationic
photoinitiators.
21. The polymerization process of claim 14 and wherein:
a) the cationic photoinitiator is selected from the to group
consisting of onium salts, organometallic salts, organosilanes,
latent sulphonic acids, triaryl sulphonium salts, ferrocenium
salts, sulphonyloxy ketones and silyl benzyl ethers.
22. The polymerization process of claim 15 and wherein:
a) the free radical photoinitiator is selected from the group
consisting of benzophenone, anthraquinone, thioxanthone, isobutyl
benzoin ether, alpha-diethoxyacetophenone and
alpha-dimethoxy-alpha-phenylacetothenone.
23. A radiation curable coating composition comprising:
a) an unsaturated nitrogen containing polyester component having at
least one group attached thereto selected from the group consisting
of maleate, fumarate, itaconate, citraconate and mesaconate;
b) a non-polymerized, co-curable vinyl ether component at least one
of separate from said unsaturated polyester component or
structurally incorporated in said unsaturated polyester component
and free radically reactive therewith;
c) a cationic photoinitiator; and
d) a free radical photoinitiator.
Description
FIELD OF THE INVENTION
The present invention relates to a polymerization process and
composition employing ultraviolet(UV) light. More particularly, the
polymerization process and composition of the present invention
includes at least one unsaturated compound containing a charge
transfer complex and a cationic photoinitiator.
BACKGROUND OF THE INVENTION
Commercialization of radiation polymerizable coatings, inks and
films requires the reactants be cured quickly and completely.
Typically, such photopolymerizable compositions contain a
photosensitive monomeric and/or polymeric material along with a
photoinitiator and adjuvant materials which provide desired
properties for the end product coating or film.
If the cure of the reactants is not complete, the residues of
unreacted starting materials migrate out of the coating following
cure. This is disadvantageous since such residues cause
contamination of the environment or otherwise render the coating
unsuitable for use in connection with products having direct food
contact. As a result, efforts have been made to develop UV curable
coating compositions that cure as quickly and completely as
possible.
It has been found that photopolymerization of a charge transfer
complex composition may be achieved with ultra-violet light and
without the need for addition of a photoinitiating compound. More
particularly, U.S. Pat. No. 5,446,073 to Jonsson et al. describes
charge transfer complexes obtained from at least one unsaturated
compound that has an electron donor group and an electron
withdrawing group. In a preferred embodiment, the specific electron
donating material is a vinyl ether and the electron withdrawing
compound is a maleamide. These compositions cure in the
absence of a photoinitiator upon subjecting the composition to
ultra-violet light having a defined wavelength.
More recently, ultra-violet curing of vinyl ether maleate systems
have been developed which incorporate free radical photoinitiators.
For example, EP 0 322 808 B1 to Friedlander et al. discloses a film
or liquid radiation curable composition comprising an ethylenically
unsaturated polyester component and ethylenically unsaturated
polyester oligomer component in a nonpolymerized vinyl ether
component together with the free radical photoinitiator.
A similar vinyl ether maleate system is disclosed in PCT/NL97/00017
to Jansen whereby the radiation curable binder comprises an
unsaturated compound containing at least one maleate and an
unsaturated compound comprising at least one vinyl ether together
with the free radical photoinitiator.
While the above systems provide a modest increase in cure time for
the reactants, each falls far short of the cure rates required for
purposes of commercialization. Further, a substantial quantity of
unreacted vinyl ether and polyester remain following irradiation
notwithstanding the use of a free radical photoinitiator. It has
been observed that as much as 20% to 40% of unreacted vinyl ether
or unsaturated polyester remains un-crosslinked in the resultant
polymeric films.
It is known to employ a cationic catalyst or photoinitiator for
copolymerization of vinyl ethers and unset polyesters. A small
amount of a Lewis Acid catalyst such as Sn Co.sub.4 will readily
polymerize vinyl monomers such as styrene butadiene, vinyl alkyl
ethers or the like. For example, U.S. Pat. No. 4,423,136 to
Crivello provides a cationic photoinitiator in connection with
ultra-violet cure of unsaturated polyesters including vinyl
ethers.
In view of the above, a need has existed in the art for an improved
photopolymerization process and composition having increased cure
rates and conversion of the reactants with a reduction in the
release of volatiles.
OBJECTS AND SUMMARY OF THE INVENTION
It is an object of the present invention to provide a
photopolymerization process and composition employing a charge
transfer complex wherein the starting materials include at least
one mono or polyunsaturated basic compound in the presence of
cationic photoinitiator and in an alternative embodiment, in the
presence of both a cationic photoinitiator and free radical
photoinitiator.
It is another object of the present invention to increase cure
times, reduce volatiles and improve polymerization of the starting
materials.
A further object of the present invention is to provide a
photopolymerization process and composition that will not
contribute to contamination of the environment and will provide
coatings and plastics that are suitable for use in connection with
products having direct contact with food.
Yet a further object of the present invention is to provide
cationic cure in the presence of mono or polyunsaturated nitrogen
containing compound.
In summary, the present invention relates to a radiation curable
coating composition comprising a charge transfer complex, the
charge transfer complex comprising at least one electron
withdrawing reactant component and at least one electron donating
reactant component that is free radically reactive therewith, the
electron withdrawing reactant component comprising an unsaturated
nitrogen containing compound and the electron donating reactant
component comprising an unsaturated compound having at least one
vinyl ether group, the electron donating reactant component may be
separate from or structurally incorporated within the electron
withdrawing reactant component and an effective amount of a
cationic photoinitiator, the cationic photoinitiator may be
combined with a free radical photoinitiator.
The present invention also relates to a photopolymerization process
comprising the steps of providing a radiation curable coating
composition comprising a charge transfer complex and effective
amount of cationic photoinitiator, the charge transfer complex
comprising at least one electron withdrawing reactant component and
at least one electron donating reactant component free radically
reactive therewith, the electron withdrawing reactant component
comprising an unsaturated nitrogen containing compound and the
electron donating reactant component comprising an unsaturated
compound having at least one vinyl ether group, the electron
donating reactant component at least one of separate from or
structurally incorporated within the at least one electron
withdrawing reactant component, applying the radiation curable
coating composition to a substrate to be coating and, subjecting
the applied radiation curable coating composition to ultraviolet
light for a period of time sufficient to polymerize the charge
transfer complex.
These and other objects of the present invention will be apparent
from the following detailed description and examples of the
invention which follow.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 illustrates conversion rates for vinyl ether and maleiates
when employing a cationic catalyst in the absence of a free radical
photoinitiator; and
FIG. 2 illustrates the conversion rates for vinyl ether and
maleiates when employing a blend of free radical photoinitiator
together with a cationic photoinitiator.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
Charge transfer complex according to the present invention
generally refers to the combination of a monounsaturated compound
which includes an electron accepting (withdrawing) group i.e.
having electron depleted double bonds, with compounds having an
electron donor properties i.e. having electron enriched double
bonds. A charge transfer complex is thereby formed by combining
each of the above-identified monounsaturated compounds or, in the
alternative, may be formed from a single bi-functional compound
which includes both the donor and the acceptor groups.
When the charge transfer complex compounds or compound is
subsequently exposed to ultra-violet radiation it will polymerize
and cure in the presence of a photoinitiator. Charge transfer
complex compounds are taught in assignee's prior U.S. Pat. No.
5,446,073 the relevant portions of which are incorporated herein by
reference.
It is within the scope of the present invention to provide multiple
unsaturated compounds, each of which contain an electron donor
group and an electron withdrawing group or, as noted above, one
unsaturated compound containing both the electron donor and the
electron withdrawing groups. A composition of the present invention
is typically liquid and capable of being cured by application of
actinic light and in particular ultra-violet light.
In a preferred embodiment of the present invention, the reactants
of the charge transfer complex comprises: an unsaturated compound
comprising at least one maleate, fumarate, itaconate, citraconate,
mesaconate group, and an unsaturated compound comprising at least
one vinyl ether group which may be separate from or structurally
incorporated within the first unsaturated component.
In a preferred embodiment, the unsaturated compound comprising at
least one maleate, fumarate, itaconate, citraconate or mesaconate
group is an unsaturated polyester resin. The unsaturated
(ethylenically unsaturated) polyester resin can be an unsaturated
polyester polymer, an unsaturated polyester oligomer or a mixture
thereof. As used herein, the term "unsaturated polyester" is meant
to be distinguished from unsaturated alkyd resins and the like.
Unsaturated polyesters of the present invention are esterification
products of ethylenically unsaturated carboxylic acids and organic
polyhydric alcohols. An unsaturated carboxylic acid having an acid
functionality of at least two, more particularly a dicarboxylic
acid or its anhydride, is utilized as a starting reactant. The
unsaturated polyester resins according to the present invention is
prepared by heating the carboxyilic component, an organic polyol
component together for about 1 to 10 hours to temperature from
about 165.degree. C. to about 250.degree. C. with water formed
during the esterification being distilled off using a sparge of an
inert gas such as nitrogen. Examples of unsaturated dicarboxylic
acids and anhydrides forming unsaturated compounds according to the
present invention are maleic acid, maleic anhydride, fumaric acid,
itaconic acid, citraconic acid, mesaconic acid.
Specific examples of unsaturated compounds having an electron
accepting group include N-alkyl maleimides, mono-and
di-cyanofumarates, maleic acid anhydride, fumaronitril, fumaric and
maleic mono and diamide derivatives. In particular, these compounds
include N-phenyl-maleimide, N-2-ethylhexylmaleimide,
N-cyclohexyl-maleimide, fumaronitril, fumaramide, dicyanofumarate
diethylester, the di-butylester of monocyano fumarate, maleic acid
anhydride, the di-butylamide of fumaric acid and maleic acid
di(ethylamide). These compounds may be attached to or incorporated
within an oligomer or a polymer such as the polyester component
noted earlier polyacrylates, polyethers, polyurethanes and
polyolefins.
In a preferred embodiment the monounsaturated compound is a polymer
or oligomer comprising at least one maleate, fumarate, itaconate,
citraconate or mesaconate group.
The unsaturated polyester according to the present invention is an
ordinary unsaturated polyester having a molecular weight between
about 800 to about 5,000. These polyesters are based upon one or
more diacids and one or more diols, the diacids are at least in
part ethylenically unsaturated diacids. As noted above, suitable
diacids include maleic acid (anhydride), fumaric acid, itaconic
acid (anhydride), citraconic acid (anhydride), mesaconic acid,
phthalic acid (anhydride), adipic acid, terephthalic acid,
isophthalic acid, malonic acid, succinic acid, glutaric acid,
sebacic acid, and 1,4-cyclohexane dicarboxylic acid and Diels Alder
products thereof.
Representative diols include, for example, ethyleneglycol,
butanediol, neopentylglycol, hexanediol, 1,4-cyclohexane diol,
1,4-cyclohexanedimethanol, propyleneglycol, diethylene glycol,
alkoxylated bisphenol-A, and alkoxylated hydrogenated
bisphenol-A.
The diacids and diols may be combined with mono-, tri- or
tetra-functional alcohols or acids. Suitable compounds include
ethylenol, butenol, 2-ethylhexanol, saturated and unsaturated fatty
acids, trimellitic acid, trimetholypropane glycerol pentaerythritol
and the like.
Separately or in combination with the unsaturated polyesters, the
unsaturated compound having the electron accepting group may be an
oligomer or a monomer. In the preferred embodiment, a maleate of
fumarate end-capped oligomer is used with one or more unsaturated
groups. In addition, monomeric species such as, for example,
dioctylmalate can be used or various other maleate or fumarate
functional compounds. Thus, the type of unsaturated compound in
general will have a molecular weight higher than about 140,
preferably higher than 200 and will have a molecular weight lower
than about 5,000 and preferably lower than 3,000 depending upon the
commercial application.
The unsaturated compound having the electron donor property
according to the present invention is a compound having a vinyl
ether component or group and includes polymers, oligomers or
monomers, the polymer, oligomer or monomer having between about 1
to about 10 vinyl ether groups.
The molecular weight of the vinyl ether compound is in general
higher than about 90 and preferably higher than about 100.
Generally speaking, the molecular weight is lower than about 5,000
and preferably lower than about 3,000.
The vinyl ether groups of the unsaturated compound containing the
at least one vinyl ether group is different from and cocurable with
the ethylenically unsaturated moieties in the backbone of the
unsaturated compound forming the electron accepting group. By
cocurable it is meant the vinyl ether groups are reactive with
ethylenic unsaturation derived from the unsaturated polyester
following exposure of the composition of the present invention to
ultra-violet light. It will be understood that when a composition
of the present invention is to be cured utilizing ultra-violet
light a photoinitiator and preferably two photoinitiators will be
combined with the composition of the present invention either prior
to or at the time of UV curing and in the manner as will be further
explained below.
Suitable examples of mono- and divinyl ether compounds include
butylvinyl ether, cyclohexyldi-methanol-divinyl ether, butyldivinyl
ether, triethylene glycol-divinylether and hydroxbutylvinyl ether
among others.
Suitable oligomers and polymers are polyurethanes having a
polyester, polyether or polycarbonate backbone and a vinylether end
group, made by reaction of hydroalkylvinylether, a polyisocyanate
and a hydroxy functional oligomer. This oligomer being a polyester,
polyether or polycarbonate having a molecular weight between about
200 and 2,000.
As noted earlier, the unsaturated compound containing the electron
accepting group may also include the electron donor group. Thus,
the unsaturated compound comprising at least one maleiate,
fumarate, itaconate, citraconate or mesaconate group and the
unsaturated compound comprising at least one vinyl ether group can
be combined into a single molecule. For example, a vinyl ether
N-polyurethane can be used which has an hydroxyfunctional
unsaturated polyester as a backbone. Dual function monomers include
the following, a hydroxy functional vinyl ether such as
hydroxybutyl vinyl ether can be reacted with an organic
diisocyanate such as isophorone diisocyanate in a stoichiometric
ratio to provide a half-capped isocyanate adduct. Thereafter,
residual isocyano functionality of the half-capped diisocyanate can
be reacted with hydroxyl functionality provided by an unsaturated
polyester polyol so as to structurally incorporate an average vinyl
ether functionality of at least two in the unsaturated polyester
component. Examples of unsaturated carboxylic acids and unsaturated
carboxylic acid anhydrides as well as organic polyols suitable for
preparing hydroxyl-functional unsaturated polyester resins include
those described herein previously. Examples of organic
diisocyanates include: toluene-2,4-diisocyanate,
toluene-2,6-diisocyanate, and mixtures thereof;
diphenylmethane-4,4'-diisocyanate,
diphenylmethane-2,4'-diisocyanate and mixtures thereof;
para-phenylene diisocyanate; biphenyl diisocyanate;
3,3'-dimethyl-4,4'-diphenylene diisocyanate;
tetramethylene-1,4-diisocyanate; hexamethylene-1,6-diisocyanate;
2,2,4-trimethylhexane-1,6-diisocyanate; lysine methyl ester
diisocyanate; bis(isocyanatoethyl)fumarate; isophorone
diisocyanate; ethylene diisocyanate; dodecane-1,12-diisocyanate;
cyclobutane-1,3-diisocyanate; cyclohexane-1,3-diisocyanate,
cyclohexane-1,4-diisocyanate and mixtures thereof; methylcyclohexyl
diisocyanate; hexahydrotoluene-2,4-diisocyanate,
hexahydrotoluene-2,6-diisocyanate and mixtures thereof;
hexahydrophenylene-1,3-diisocyanate,
hexahydrophenylene-1,4-diisocyanate and mixtures thereof;
perhydrodiphenylmethane-2,4'-diisocyanate,
perhydrodiphenylmethane-4,41-diisocyanate and mixtures thereof. The
resulting unsaturated polyester component (also now containing
urethane moieties), and having an average vinylether functionality
of at least two, usually is free of unreacted NCO groups.
Optionally, a liquid, radiation curable composition of the
invention additionally may contain other ethylenically unsaturated
monomers or oligomers examples of which include: other vinyl
monomers such as vinyl acetate, styrene, vinyl toluene, divinyl
benzene, methylvinyl ether, ethylvinyl ether and butylvinyl ether;
acrylic and methacrylic esters such as methyl (meth)acrylate, ethyl
(meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate,
isobutyl (meth)acrylate, 2-ethylhexyl (meth) acrylate,
2-hydroxyethyl (meth)acrylate, glycidyl (meth)acrylate, ethylene
glycol di(meth)acrylate, diethylene glycol di(meth)acrylate,
tetraethylene glycol di(meth)acrylate, glycerol di(meth)acrylate,
glycerol tri(meth)acrylate, 1,3-propylene glycol di(meth)acrylate,
dipropylene glycol di(meth)acrylate, 1,4-butanediol
di(meth)acrylate,
1,2,4-butanetriol tri(meth)acrylate, 1,6-hexanediol
di(meth)acrylate, 1,4-cyclohexanediol di(meth)acrylate,
1,4-benzenediol di(meth)acrylate, pentaerythritol
tetra(meth)acrylate, 1,5-pentanediol di(meth)acrylate,
trimethylolpropane di(meth)acrylate, trimethylolpropane
tri(meth)acrylate,
2,2-dimethyl-3-hydroxypropyl-2,2-dimethyl-3-hydroxypropionate,
isobornyl (meth)acrylate and tetrahydrofurfuryl (meth)acrylate;
(meth)acrylates derived from aromatic glycidyl ethers such as
bisphenol-A-diglycidyl ether and aliphatic glycidyl ethers such as
butanediol diglycidyl ether, specific examples of which include
1,4-butanediol diglycidylether di(meth)acrylate,
bisphenol,-A-diglycidylether di(meth)acrylate and neopentylglycol
diglycidylether di(meth)acrylate; and acrylic or methacrylic amides
such as (meth)acrylamide, diacetone (meth)acrylamide,
N(beta-hydroxyethyl) (meth)acrylamide, N,N-bis(beta-hydroxyethyl)
(meth)acrylamide, methylene bis(meth)acrylamide, 1,6-hexamethylene
bis(meth)acrylamide, diethylenetriamine tris(meth)acrylamide,
bis(gamma-(meth)acrylamidepropoxy) ethane and beta-(meth)acrylamide
ethylacrylate.
Charge transfer complex compounds within the scope of the present
invention further include those taught in International Application
No. WO 98/11151 and Application No. WO 98/11152 both applications
of which are incorporated herein by reference.
For example, the present invention includes a polymerizable
composition, characterized by at least one compound selected among
the polymers functionalized by maleimide groups and consisting of
products obtained by reaction of at least one maleic anhydride
represented by formula: (I): ##STR1## wherein each of R.sup.1 and
R.sup.2 represents independently H, a C.sub.1 -C.sub.12 alkyl group
such as methyl, or a halogen such as chlorine; at least one
compound (II) having at least one --NH.sub.2 function and at least
another function selected among --OH, --NH.sub.2, --NH--, --COOH
and --COOR.sup.3, R.sup.3 representing a C.sub.1 -C.sub.5 alkyl
group; and at least one compound (III) selected among polyols,
mono- or polyfunctional epoxy, polyisocyanates and polyamines; the
compound (II) having reacted first with the maleic anhydride in
order to open maleic anhydride rings, among others, in order to
form maleamic acid functions by opening the maleic anhydride rings
by the primary amine function of compound (II), the maleamic acid
functions having then being at least partially closed again into
maleimide rings by heating; the maleimides so produced having
reacted with the compound(s) (III) and/or with at least one
polyacid and/or one cyclic anhydride (IV), added to the reaction
medium after opening of the maleic by anhydride compound (II), and
the chain of the polymer having been formed by polycondensation
and/or polyaddition reactions having involved the compound(s) (III)
and the compound(s) (IV) as added, and/or in case where it would be
remained an excess of the maleic anhydride (I) after opening of
compound (I) by (II), the excess of maleic anhydride (I), and the
uncyclized products being also entered into the composition of the
chain; the compounds (III) involved being furthermore selected
among: in case where they are intended to react with an anhydride
(IV) and/or with the excess of anhydride (I): at least one polyol
and/or at least one mono- or polyfunctional epoxy and/or at least
one polyamine, and possibly at least one polyisocyanate; in case
where they are intended to react with a diacid (IV): at least one
polyol and/or at least one mono- or polyfunctional epoxy and/or at
least one polyamine, and possibly at least one polyisocyanate; or
at least one polyisocyanate; and in case where the compound (II)
includes a --COOR.sup.3 function: at least one polyol.
Preferably, the anhydride of formula (I) is maleic anhydride.
The compounds (II) are especially selected among the compounds
represented by the formulas H.sub.2 N--A--OH, H.sub.2 N--A--COOH,
H.sub.2 N--A--COOR.sup.3 and H.sub.2 N--A--NH.sub.2, wherein A
represents a straight, branched or cyclic alkylene group, or an
arylene group, it being possible for the groups to be interrupted
by oxygen or sulfur atoms, or by --NR.sup.4 -- groups, wherein
R.sup.4 represents hydrogen or alkyl. Examples of the compounds
(II) include aminoalcohols, such as ethanolamine, propanolamine,
isopropanolamine, 2-(2-aminoethoxy)ethanol,
N-(2-amino-ethyl)ethanolamine; aminoacids, such as valine,
p-amino-benzoic acid, alanine, 2-aminohexanoic acid,
6-aminohexanoic acid, 7-aminoheptanoic acid, 2-aminoisobutyric
acid; methyl or ethyl esters of the abovementioned aminoacids;
diamines, such as ethylenediamine,
2-methyl-1,5-pentamethylenediamine, hexamethylenediamine, 2,2,4-
and/or 2,4,4-trimethylhexamethylenediamine, dodecamethylenediamine,
5-methylnonamethylenediamine, decamethylenediamine,
isophoronediamine, bis(4-aminocyclohexyl)methane,
bis(3-methyl-4-aminocyclohexyl)methane,
bis(3-methyl-4-amino-5-ethylcyclohexyl)methane,
1,2-bis(4-aminocyclohexyl)-ethane,
2,2'-bis(4-aminocyclohexyl)propane,
2,2'-bis(3-methyl-4-aminocyclohexyl)propane,
4,7-dioxadecane-1,10-diamine, 4,9-dioxadodecane-1,12-diamine,
4,7,10-trioxatridecane-1,13-diamine; and polyoxyethylenated and/or
polyoxypropylenated di- or triamines sold under the tradename
"Jeffamine.RTM.".
Trifunctional compounds (II) such as L-serine, 3-hydroxy 4-amino
benzoic acid and 3-amino 4-hydroxy benzoic acid and other triamines
such as N-(2-aminoethyl)-1,2-ethanediamine and
N-(3-aminopropyl)-1,3-propanediamine, are also included.
The polyols (III) are preferably diols or triols, it is within the
scope of the present invention for polyols of higher functionality
(pentaerythritol for example) to be present in small amounts. As
examples of diols or triols, propylene glycol, dipropylene glycol,
diethylene glycol, ethylene glycol, 1,3-butanediol, 1,4-butanediol,
neopentyl glycol, triethylene glycol, tripropylene glycol, butylene
glycol, glycerol, trimethylol propane, 1,6-hexanediol,
1,4-cyclohexane diol, 1,4-cyclohexane dimethanol,
2-methyl-1,3-propane diol, 2-butyl-2-ethyl-1,3-propane diol,
1,2-bis(hydroxyethyl)cyclohexane,
4'-(2-hydroxyethoxy)-2,2-dimethyl-2-hydroxyacetophenone,
2,2-dimethyl-3-hydroxypropyl-2,2-dimethyl-3-hydroxypropionate,
dibromoneopentylglycol can be mentioned. Monoalcohols may be added
in small amounts.
The epoxy compounds (III) are generally mono- and diepoxy
compounds, among which epichlorhydrine,
7-oxa-bicyclo[4.1.0]heptane, 3,4-epoxycyclohexylmethyl
3,4-epoxycyclohexane carboxylate, bisphenol A diglycidyl ether,
1,2-epoxyhexadecane, 3,3,3-trichloropropylene oxide and allyl
glycidyl ether.
The polyisocyanates (III) are, above all, diisocyanates, such as
4,4'-diphenylmethane diisocyanate, trimethylhexamethylene
diisocyanate, toluene diisocyanate, isophoronediisocyanate,
tetramethylene diisocyanate, pentamethylene diisocyanate,
4,4'-dicyclohexylmethane diisocyanate,
2,2,4-trimethylhexamethylene-1,6-diisocyanate,
triphenylmethane-4,4',4"-triisocyanate, polymethylene
polyphenylisocyanate, m-phenylene diisocyanate, p-phenylene
diisocyanate, 1,5-naphthalene diisocyanate,
naphthalene-1,4-diisocyanate, diphenylene-4,4'-diisocyanate,
3,3'-bi-tolylene-4,4'-diisocyanate, 1,4-cyclohexylene dimethylene
diisocyanate, xylylene-1,4-diisocyanate, xylylene-1,3-diisocyanate,
cyclohexyl-1,4-diisocyanate and
3,3'-dimethyldiphenylmethane-4,4'-diisocyanate.
Preferably, the polyamines (III) are diamines, such as ethylene
diamine, 2-methyl-1,5-pentamethylene diamine,
trimethylhexane-1,6-diamine, hexamethylenediamine, 2,2,4- and/or
2,4,4,-trimethylhexamethylenediamine, dodecamethylenediamine,
trimethylhexamethlenediamine, 5-methylnonamethylenediamine,
decamethylenediamine, isophoronediamine,
bis(4-aminocyclohexyl)methane,
bis(3-methyl-4-aminocyclohexyl)methane,
bis(3-methyl-4-amino-5-ethylcyclohexyl)methane,
1,2-bis(4-aminocyclohexyl)ethane,
2,2'-bis(4-aminocyclohexyl)propane and
2,2'-bis(3-methyl-4-aminocyclohexyl)propane.
As primary examples of polyacids (IV) and as noted earlier,
diacids, such as maleic, fumaric, chloromaleic, citraconic,
metaconic, itaconic, tetraconic, orthophthalic, isophthalic,
terephthalic, succinic, methylsuccinic, adipic, sebacic,
tetrabromophthalic, tetrachlorophthalic, glutaric, pimelic acids or
the like, are within the scope of the present invention.
The cyclic anhydrides (IV) employed, which are unsaturated or
saturated, may be selected among maleic anhydride, succinic
anhydride, phthalic anhydride, trimellitic anhydride,
tetrahydrophthalic anhydride, hexahydrophthalic anhydride,
chlorinated anhydrides such as chlorendic anhydride,
tetrachlorophthalic anhydride and tetrabromophtalic anhydride,
methyltetrahydrophthalic anhydride, nadic anhydride, methyl nadic
anhydride, itaconic anhydride, citraconic anhydride, and glutaric
anhydride. Maleic anhydride and succinic anhydride are particularly
mentioned. An anhydride including a photoinitiator moiety, such as
3,3',4,4'-benzophenonetetracarboxylic anhydride, may be used in
some applications. The polymerizable composition characterized by
at least one compound selected among the polymers functionalized by
maleimide groups have a number average molecular weight between
about 350 and about 5000, and especially between about 500 and
about 3000 (as measured by GPC, polystyrene standard). Furthermore,
they include generally about 0.02 to about 5 maleimide functions,
especially 0.2 to 2 maleimide functions, by kg of polymer
(mass).
Preparation of the polymers functionalized by maleimide groups
according to the present invention can be carried out generally as
follows. At least one compound (I), at least one compound (II) and
at least one compound (III), the compounds (I), (II) and (III), are
reacted under conditions that permit compound (II) to react first
with the maleic anhydride (I), thereby opening the maleic anhydride
rings, among others, in order to form maleamic acid functions by
opening the maleic anhydride rings by the primary amine function of
the compound (II), then to close again at least partially the
maleamic acid functions into maleimide rings, by heating, the
maleimides so formed reacting with the compound(s) (III) and/or
with (IV) at least one polyacid and/or one cyclic anhydride which
are added to the reaction medium after opening of (I) by (II), and
the chain of the polymer thereby being formed by polycondensation
and/or polyaddition reactions involving the compound(s) (III) and
said compound(s) (IV) as added and/or, in case where it would
remain an excess of maleic anhydride after opening of (I) by (II),
the excess of maleic anhydride (I) and with the uncyclized products
also entering into the composition of the chain.
According to this process, in a first step, at least one maleic
anhydride (I) is reacted with at least one compound (II) in a polar
solvent medium in order to open the anhydride rings. In the second
step, a ring forming reaction is conducted by heating the reaction
medium obtained at the end of the first step, possibly in the
presence of at least one cyclic anhydride (IV), wherein the ring
forming reaction results in at least partly closing the anhydride
rings which were opened in the previous step, in order to give a
product of at least partly ring forming reaction which comprises
maleimides N-substituted by groups functionalized by --OH or --COOH
or --COOR.sup.3 or --NH.sub.2 or --NH-- according to the compound
(s) (II) used, in case where the ring forming reaction has been
conducted in the absence of any cyclic anhydride (IV), or
maleimides N-substituted by groups functionalized by --COOH or
--COOR.sup.3 with formation of the diacid corresponding to said
cyclic anhydride (IV), possibly in mixture with the excess of
anhydride (IV) not reacted, in case where the ring forming reaction
has been conducted in the presence of cyclic anhydride (IV); and in
a third step, the product of the at least partly ring forming
reaction is entered into a polycondensation and/or polyaddition
reaction with the at least one compound (III) as earlier defined
above.
At the first step, the maleic anhydride rings are opened by at
least a part of --NH2,--NH-- or OH functions of compound(s) (II),
the opening by --NH.sub.2 functions leading to maleamic acid
functions: ##STR2##
Dependant upon the type of compound (II) selected, the opening of
one or more maleic anhydride rings by compound (II) is obtained.
The COOH or COOR.sup.3 functions of compound(II), if present,
remain free.
This first step may be conducted at a temperature of about 0 to
80.degree. C., and particularly 0 to 20.degree. C., during 1 to 10
hours, and especially during 1 to 3 hours, within a polar solvent
such as acetone, ethanol, chloroform, dichloromethane,
tetrahydrofuran, cyclohexanone, dioxane, methylethylcetone, ethyl
acetate among others.
The stoechiometry for this reaction is not essential to the present
invention. However, a stoechimetry corresponding to a molar ratio
(I)/(II) higher than or equal to 1, may be preferred. It is also
possible to proceed with a stoechimetry corresponding to a maleic
anhydride function for each NH.sub.2, OH or NH function of
compounds (II). When the maleic anhydride (I) is introduced in
excess, the maleic anhydride unconsumed at this step is then fed at
the third step. In that situation, if no cyclic anhydride (IV) is
added at the second step, the second step is conducted by
continuing the heating and the third step by further continuing the
heating and, following evaporation of the solvent, addition of
compound (III), for example a polyol. However, according to a
further variant of the invention, the latter could be added at the
beginning.
Before starting the second step (at least partial cyclization),
except if the same solvent is maintained, the polar solvent of the
first step is removed in general by evaporation. Otherwise, the
solvent may be recycled.
In the case where the second step is conducted in the presence of
cyclic anhydride [(IV) and/or an excess of (I)], it is conducted
generally at a temperature of about 40 to 160.degree. C., and
especially of 80 to 120.degree. C., during 0.5 to 10 hours,
especially during 1 to 6 hours, in an aprotic solvent such as
toluene and xylene. This can also be conducted in the absence of
any solvent; the excess of anhydride could be considered as acting
as a solvent.
In the case where the second step is conducted in the absence of
anhydride, it is conducted generally at a temperature of 40 to
160.degree. C., especially of 80 to 110.degree. C., during 0.5 to
10 hours, especially during 3 to 7 hours, in a solvent of the same
acid as obtained in the first step. Ethanol and methanol are
representatives examples.
The solvent which would be used in this step is then generally
evaporated and or recycled.
The polycondensation and/or polyaddition reactions of this third
step are conventional reactions and known to those of ordinary
skill in the art.
In the case of a reaction with at least one polyol and/or one epoxy
and/or one polyamine, and possibly with (IV) at least one polyacid
or one anhydride, this third step can conducted at a temperature of
150 to 250.degree. C.
The beginning of the reaction is generally conducted at the
atmospheric pressure, the end being possibly conducted under
reduced pressure.
In the case of a reaction with a polyioscyanate, and, possibly,
with at least one polyacid and/or one anhydride and/or one polyol
and/or one epoxy and/or one polyamine, the third step may be
conducted at a temperature of 20 to 200.degree. C.
In case where the second step is conducted in the presence of
anhydride [(IV) or excess of (I)], it is possible to add at the
third step a polyisocyanate and a polyol or epoxy and/or a
polyamine, with possibly a polyacid (IV); in case where the second
step is conducted in the absence of anhydride, it is possible at
the third step to add either a polyisocyanate alone, either a
polyisocyanate and a polyol and/or a polyamine and/or a
polyacid.
If there are esterification reactions (acid +alcohol) or
amidification reactions (acid +amine) and addition reaction, the
esterification and/or amidification reactions are carried out first
between 150 and 250.degree. C., then the addition reactions are
carried out (isocyanate+alcohol or acid or amine), at temperatures
lower than 150.degree. C.
Otherwise, in a preliminary step, the double bond ##STR3## of the
anhydride (I) may be protected by a reaction with a protecting
agent such as furan or cyclopentadiene, the deprotection being
carried out at a time from the second step under the action of
heat.
Consequently, this process as set forth above may be a "one pot"
process,
that does not require isolation of the reaction products after each
step, the only measure to be taken after the first and second steps
being the evaporation of the solvent.
According to a second embodiment of the process according to the
present invention, which is also a "one-pot" process and
advantageously without any solvent, the at least one compound (I),
at least one compound (II) and at least one polyol and/or epoxy
and/or polyamine (III), and possibly at least one polyacid and/or
one cyclic anhydride (IV) are reacted by heating a mixture of these
compounds at a temperature of 180 to 200.degree. C., with removing
the possible condensation water, the compound (I) being introduced
preferably in a stoechimetric excess with respect to compound (II),
the compound(s) (III) and the polyacid(s) and/or anhydride(s) (IV)
being introduced simultaneously with the compounds (I) and (II) or
at a later stage. The mixture can be heated to the above mentioned
temperature either directly or stepwise.
If a polyisocyanate is used in a "one-pot" process without any
solvent, according to another embodiment of this invention, a
polyacid (IV) and a polyisocyanate (III) are added to the mixture
of compounds (I) and (II) without any solvent, possibly after
compounds (I) and (II) have been reacted and the reaction is
conducted at a temperature of 40 to 160.degree. C., the compound
(I) being introduced preferably in a stoechiometric excess with
respect to compound (II).
And according to yet another variant of this invention, to a
mixture of compounds (I) and (II) without any solvent, is added a
polyol and/or an epoxy and/or a polyamine (III), in excess with
respect to compound (I) if it remains compound (I) in a free state
or with respect to polyacid (IV) which is added in case of need,
and the esterification reaction is conducted between 150 and
250.degree. C., then the mixture is heated to a temperature lower
than 150.degree. C., a polyisocyanate (III) is added, and the
alcohol/isocyanate reaction is conducted at that temperature.
The composition according to the present invention may optionally
further comprise at least one compound (A') selected among
N-substituted maleimides, represented by the formula: ##STR4##
wherein R is an alkyl, arylalkyl, aryl or alkylaryl radical, having
especially from 1 to 12 carbon atoms. Examples of these maleimides
are N-ethylmaleimide, N-isopropylmaleimide, N-n-butylmaleimide,
N-isobutylmaleimide, N-tert.-butylmaleimide, N-n-octylmaleimide,
N-cyclohexylmaleimide, N-benzylmaleimide and N-phenylmaleimide.
The at least one compound (B) making part of the composition
according to the present invention is advantageously selected among
compounds represented by the formula (V): ##STR5## wherein each of
R.sup.5, R.sup.6 and R.sup.7 represents independently hydrogen or
an aliphatic group, preferably a C.sub.1 -C.sub.12 alkyl group,
such as methyl, ethyl and propyl; and R.sup.8 represents an
aliphatic group or an aromatic group, optionally substituted for
example by OH compounds represented by the formula (VI): ##STR6##
wherein each of R.sup.9, R.sup.10 and R.sup.11 represents
independently hydrogen or an aliphatic group, preferably a C.sub.1
-C.sub.12 alkyl group, such as methyl, ethyl and propyl; and
R.sup.12 is a n-valent residue of an organic polyol; n is an
integer from 2 to 6; N-vinyl pyrrolidone, N-vinyl imidazole,
2-vinyl pyridine, N-vinylcarbazole, N-vinyl caprolactam,
paramethoxystyrene, isoeugenol, 4-propenyl-anisole, monobutyl
4-vinylbutoxy carbonate, monobutyl 4-propenyl butoxycarbonate,
N-vinyl-formamide and its derivatives.
As preferred compounds of formula (V), the following monofunctional
vinylethers can be mentioned: methyl vinyl ether, ethyl vinyl
ether, butyl vinyl ether, isobutyl vinyl ether, octadecyl vinyl
ether, 4-hydroxybutyl vinyl ether, dodecyl vinyl ether.
As preferred compounds of formula (VI), the following
polyfunctional vinylethers, in particular those obtained in a known
manner from a di-, tri- or tetrafunctional organic diol, acetylene
and a basic catalyst under high pressure can be mentioned. These
include, for example, triethylene glycol divinyl ether,
tripropylene glycol divinyl ether, diethylene glycol divinyl ether,
1,4-butanediol divinyl ether, tetraethylene glycol divinyl ether,
cyclohexanedimethanol divinylether, bis(4-vinyloxybutyl)succinate,
bis(4-vinyloxymethyl-cyclohexylmethyl)glutarate,
1,3-benzenedicarboxylic acid, bis[4-(ethenyloxy)butyl]ester.
The composition according to the invention can also include at
least one component selected among a monomer or oligomer reactive
diluent, a non reactive solvent or diluent, and an usual additive
such as a pigment.
As examples of monomer or oligomer reactive diluent, the following
compounds are representative and include vinyl monomers, such as
vinyl acetate, styrene, vinyl toluene, divinyl benzene; acrylic and
methacrylic esters, such as methyl (meth)acrylate, ethyl
(meth)acrylate, isopropyl (meth) acrylate, n-butyl (meth)acrylate,
isobutyl (meth)acrylate, 2-ethylhexyl (meth)acrylate,
2-hydroxyethyl (meth)acrylate, glycidyl (meth)acrylate, ethylene
glycol di(meth)acrylate, diethylene glycol (di)methacrylate,
tetraethylene glycol di(meth)acrylate, glycerol di(meth)acrylate,
glycerol tri(meth)acrylate, 1,3-propylene glycol di(meth) acrylate,
dipropylene glycol di(meth)acrylate, tripropylene glycol
di(meth)acrylate, 1,4-butanediol di(meth)acrylate,
1,2,4-butanetriol tri(meth)acrylate, 1,6-hexanediol
di(meth)acrylate, 1,4-cyclohexanediol di(meth)acrylate,
1,4-benzenediol di(meth)acrylate, pentaerythritol
tetra(meth)acrylate, 1,5-pentanediol di(meth)acrylate,
trimethyolpropane di(meth)acrylate, trimethylolpropane
tri(meth)acrylate,
2,2-dimethyl-3-hydroxypropyl-2,2-dimethyl-3-hydroxy-propionate,
isobornyl (meth)acrylate and tetrahydrofurfuryl (meth)acrylate;
(meth)acrylates derived from aromatic glycidyl ethers such as
bisphenol A-diglycidyl ether and derived from aliphatic glycidyl
ethers such as butandediol diglycidyl ether, specific examples of
them comprising 1,4-butanediol diglycidylether di(meth)acrylate,
bisphenol A-diglycidylether di(meth)acrylate and neopentrylglycol
diglycidylether di(meth)acrylate; and acrylic or methacrylic amides
such as (meth)acrylamide, diacetone (meth)acrylamide,
N(beta-hydroxyethyl) (meth)acrylamide, N,N-bis(beta-hydroxyethyl)
(meth)acrylamide, methylene bis(meth)acrylamide, 1,6-hexamethylene
bis(meth)acrylamide, diethylenetriamine tris(meth)acrylamide,
bis(gamma-(meth)acrylamidepropoxy) ethane and beta-(meth)
acrylamide ethylacrylate.
As examples of non reactive solvent or diluent, the following
compounds can be cited: ethyl acetate, butyl acetate,
methoxypropanol, isopropanol, methyl ethyl ketone, acetone.
The charge transfer complex systems as set forth above will further
include an effective amount of cationic photoinitiator.
Various types of cationic photoinitiators are suitable. Both ionic
cationic photoinitiators such onium salts or organometallic salts
are suitable as well as non-ionic cationic photoinitiators such as
organosilanes, latent sulphonic acids and the like. Preferred are
photosensitive onium salts, in particular, onium salts such as
those disclosed in U.S. Pat. Nos. 4,058, 4,138,255, 4,161,478,
4,175,972, all of which are hereby incorporated by reference.
Triaryl sulphonium salts are most preferred, in particular triaryl
sulphonium salts such as those sold by Union Carbide under the
tradename Cyracure UVI 6990 and 6974. Also suitable are ferrocenium
salts such as those sold under the Irgacure tradename by
Ciba-Geigy, in particular Irgacure 261. Sulphonyloxy ketones and
silyl benzyl ethers are also good cationic photoinitiators. A
detailed analysis of the mechanism of cationic curing is disclosed
in "Photosensitized Epoxides as a Basis for Light-Curable Coatings"
by William R. Watt, American Chemical Society Symposium, Ser. 114,
Epoxy Resin Chemistry, Chapter 2, 1979, and in "Chemistry and
Technology of UV and EB Formulation for Coatings, Inks and Paints",
Volume 3, entitled "Photoinitiators for Free Radical and Cationic
Polymerization, K. K. Dietliker, pages 332-374 (1991), both of
which are hereby incorporated by reference. Photosensitive onium
salts are used as photoinitiators in cationic curing, in
particular, onium salts such as those disclosed in U.S. Pat. Nos.
4,058,401, 4,138,255, 4,161,478, 4,175,972, all of which are hereby
incorporated by reference. Triaryl sulphonium salts are most
preferred, in particular sulphonium salts such as those sold by
Union Carbide under the tradename Cyracure UVI 6990 and 6974.
In a preferred embodiment of the present invention as set forth
above, a second photoinitiator, namely a free radical
photoinitiator is added either prior to or during the curing step.
Examples of free radical photoinitiators include benzophenoe,
anthraquinone, thioxanthone, isobutyl benzoin ether, mixers of
butyl isomers of butyl benzone ether, alpha,
alpha-diethoxyacetophenone, and alpha,
alpha-dimethoxy-alpha-phenylacetothenone. Other examples of free
radical photoinitiators according to the present invention include
those as set forth in U.S. Pat. No. 4,017,652, the relevant
portions of which are incorporated herein by reference.
While the curing times achieved with the use of a single cationic
photoinitiator according to the present invention are faster than
that shown in the prior art, exceptionally fast curing times can be
obtained and a marked increase in conversion of the reactant
materials over that known in the prior art may be achieved when the
cationic photoinitiator is combined with a free radical
photoinitiator. Unexpectedly, the maleiate or the maleimide or
other nitrogen (basic) containing groups of the reactant materials
do not poison the cationic photoinitiator or catalyst and in fact
are caused to be more completely cured and at a faster rate than
previously known. Combining the cationic photoinitiator with the
free radical photoinitiator greatly increases the conversion rates
of all the starting materials and substantially reduces the amount
of unreacted starting materials following polymerization. A
cationic photoinitiator in combination with a free radical
photoinitiator according to the present invention provides the best
results for conversion of the reactant products.
In a preferred embodiment, the free radical photoinitiator
comprises from about 0.5% by weight to about 1% by weight of the
total composition and the cationic photoinitiator comprises from
about 1% by weight to about 3% by weight of the total
composition.
Pursuant to the present invention the composition is subjected to
ultra-violet light to cause polymerization thereof. The
ultra-violet light is preferably a high intensity light to provide
a dosage of at least 200 millejoules per square centimeter of
surface area of the composition being polymerized. In the event
that lower energy is to be employed, it is then desired to subject
the compositions also to elevated temperatures in order to reduce
the time for adequate polymerization to occur.
Suitable lamps employed to provide the desired intensity and
availability of wavelength and spectro distribution include that
available from Fusion Systems, Corp. of Gaithersburg, Md. under the
trade designation F-450 Model with a D bulb. A description of lamps
suitable for the present invention need not be described herein in
any detail since such can be provided by those skilled in the art
without undue experimentation. For example, the lamp disclosed in
U.S. Pat. No. 4,042,850 to Ury et al. which is incorporated herein
by reference may be used.
Ultra-violet radiation from other suitable sources which emit
ultra-violet light having a wavelength between about 180 and 400
nanometers may be employed to cure the composition in the present
invention. Additional sources of ultra-violet light are generally
known and include for example mercury arcs, carbon arcs, low
pressure mercury lamps, medium pressure mercury lamps, high
pressure mercury lamps, swirl-flow plasma arcs and ultra-violet
light emitting diodes. Preferred are ultra-violet light emitting
lamps of the medium pressure mercury vapor type. Such lamps usually
have fuse cords envelopes and are ordinarily in the form of long
tubes having an electrode at both ends.
If desired, the compositions of the present invention may also
contain pigments. The pigment is typically an ultra-violet light
transparent pigment meaning the pigment does not substantially
interfere with Ultra-violet curing of the composition. Examples of
ultra-violet light transparent pigments include talc, calcium
carbonate, aluminum silicate, magnesium silicate and barytes.
The radiation curable compositions of the present invention are
especially useful as radiation curable coating compositions. They
can be applied to a variety of substrates, examples of which
include wood, paper, particle board, chip board, metals, metals
having primers thereon, glass, plastics and metalized plastics. The
radiation curable compositions may be applied by any known means
including brushing, dipping, roll coating, spraying, curtain
coating and the like. They may be preliminarily dried to remove
solvent as desired and then cured by radiation.
The following examples illustrate the present invention and its
preferred embodiments without limiting the scope thereof. As used
in the body of the specification, examples and claims all percents,
ratios and parts are by weight unless otherwise indicated.
In each of the examples, unsaturated polyesters were obtained from
commercial sources. The copolymers were prepared from maleic
anhydride and glycols such as propylene glycol. The polyesters were
blended with vinyl ethers of either butonediol divinyl ether or
triethylene glycol divinyl ether. In particular, maleimide
unsaturated polyesters were obtained from Cray Valley, France and
are of type described in Internation Application Nos. WO 98/11151
and WO 98/11152. The endcapped maleimide unsaturated polyesters
were diluted with butanediol divinyl ether or triethyleneglycol
divinyl ether.
EXAMPLE 1
A Cray Valley maleimide unsaturated polyester (100 gms) vinyl ether
system (UPEMI) was diluted with 0.1% of BYK 333 surfactant. Draw
downs were made on steel Q panels employing wire wound draw down
rods. Film thickness of 0.5, 1.0 and 2.0 mils were tested and cured
at a line speed of 1 pass or 2 passes at 15 ft/min. The coatings
were cured using a F-600 microwave lamp equipped with an H
bulb.
The photoinitiator-free cured coatings were then evaluated as to
Pencil Hardness, Koning Pendulum Hardness, methyl ethyl ketone(MEK)
resistance and cotton ball surface tack. The results are set forth
in Table I.
TABLE 1
__________________________________________________________________________
Curing of the Cray Valley UPEMi polyester without photoinitiator
Film Line Pencil Hardness Pendulum Koning MEK Surface Thickness
Speed 1 hr 24 hrs 5 days 1 hr 24 hrs 5 days 1 hr Tack
__________________________________________________________________________
0.5 mils 1 .times. 15 FPM HB H H -- -- -- -- OK 0.5 mils 2 .times.
15 FPM HB H H -- -- -- -- OK 1.0 mils 1 .times. 15 FPM F H H -- --
-- -- OK 1.0 mils 2 .times. 15 FPM F H H -- -- -- -- OK 1.0 mils 1
.times. 15 FPM F H 2H 27 32 52 +100 OK 1.0 mils 2 .times. 15 FPM F
H 2H 35 44 86 +100 OK
__________________________________________________________________________
EXAMPLE 2
The same polymer system as set forth in Example 1 was employed
together
with a photinitiator comprising a 50-50% mix of Irgacure 1173 and
Irgacure 184. The photinitiator mix was added at 1 and 2% to the
UPEMi polyester. Pencil hardness, Koning pendulum hardness, MEK
resistance and surface hardness data were compiled and are Table
2.
TABLE 2
__________________________________________________________________________
Curing of UPEMi with Free Radical Photoinitiator Film Line Pencil
Hardness Koning Pendulum MEK Surface Thickness Speed 1 hr 24 hrs 5
days 1 hr 24 hrs 5 days 1 hr Tack
__________________________________________________________________________
1.0% 0.5 mils 60 H 2H 2H -- -- -- -- OK 0.5 mils 90 H 2H 2H -- --
-- -- OK 1.0% 1.0 mils 60 H 2H 2H -- -- -- -- OK 1.0 mils 90 H 2H
2H -- -- -- -- OK 1.0% 2.0 mils 60 H 2H 2H 44 64 75 +100 OK 2.0
mils 90 H 2H 2H 33 49 58 +100 OK 2.0% 0.5 mils 60 H 2H 2H -- -- --
-- OK 0.5 mils 90 H 2H 2H -- -- -- -- OK 2.0% 1.0 mils 60 H 2H 2H
-- -- -- -- OK 1.0 mils 90 H 2H 2H -- -- -- -- OK 2.0% 2.0 mils 60
H 2H 2H 56 77 92 +100 OK 2.0 mils 90 H 2H 2H 46 59 80 +100 OK
__________________________________________________________________________
EXAMPLE 3
The polymer system as set forth in Example 1 was provided and added
to the system was a free radical photoinitiator (1:1 blend of 1173
and 184) and a cationic photoinitiator UVI-6974.
______________________________________ MIX I MIX - II
______________________________________ UPEMi (stock solution) 100
100 PI mix (1173:184) .5 1.0 UVI-6974 1.0 2.0
______________________________________
The resultant polymers films were coated on Q panels at thickness
of 0.5, 1.0 and 2.0 mils. The films were cured at 60 or 90 FPM line
speeds. The results are listed in Table 3.
TABLE 3
__________________________________________________________________________
Use of Free Radical and Cationic Photoinitiator with the Maleimide
Vinyl Ether System Film Line Pencil Hardness Koning Pendulum MEK
Thickness Speed 1 hr 24 hrs 5 days 1 hr 24 hrs 5 days 1 hr Tack
__________________________________________________________________________
0.5 mils 60 FPM F 2H 2H -- -- -- -- OK 0.5 mils 90 FPM F 2H 2H --
-- -- -- OK 1.0 mils 60 FPM F 2H 2H -- -- -- -- OK 1.0 mils 90 FPM
F 2H 2H -- -- -- -- OK 2.0 mils 60 FPM HB 2H 2H 39 63 72 +100 OK
2.0 mils 90 FPM HB 2H 2H 33 53 58 +100 OK 0.5 mils 60 FPM F 2H 2H
-- -- -- -- OK 0.5 mils 90 FPM F 2H 2H -- -- -- -- OK 1.0 mils 60
FPM F 2H 2H -- -- -- -- OK 1.0 mils 90 FPM F 2H 2H -- -- -- -- OK
2.0 mils 60 FPM HB 2H 2H 34 66 75 +100 OK 2.0 mils 90 FPM HB 2H 2H
37 53 67 +100 OK
__________________________________________________________________________
EXAMPLE 4
Three separate formulations were prepared from the stock solution
of the UPEMi polymer-vinyl ether mixture as set forth in the above
examples to which were added 1%, 2% and 3% by weight of cationic
photoinitiator UVI 6974 (triarylsulphoniumhexchloride
initiator).
______________________________________ Mix I Mix II Mix III
______________________________________ UPEMi Stock Solution 99% 98%
97% UVI 6974 1% 2% 3% ______________________________________
The formulations were coated onto Q steel panels at thickness
values of 0.5, 1.0 and 2.0 mils. The films were cured at line
speeds of 60 and 90 feet per minute using a F-600-H. The results
appear in Table IV.
TABLE 4
__________________________________________________________________________
Curing of the UPEMi maleimide vinyl ether system with cationic
catalyst Film Line Pencil Hardness Koning Pendulum MEK Thickness
Speed 1 hr 24 hrs 5 days 1 hr 24 hrs 5 days 1 hr 24 hr 5 days
__________________________________________________________________________
0.5 mils 60 FPM HB H H -- -- -- 17 35 65 0.5 mils 90 FPM B F H --
-- -- 17 25 37 1.0 mils 60 FPM HB H H -- -- -- 47 +100 +100 1.0
mils 90 FPM B F H -- -- -- 28 60 +100 2.0 mils 60 FPM HB H H 22 35
36 +100 +100 +100 2.0 mils 90 FPM B F H 18 30 31 +80 +100 +100 0.5
mils 60 FPM HB H H -- -- -- 34 65 77 0.5 mils 90 FPM B F H -- -- --
24 50 66 1.0 mils 60 FPM HB H H -- -- -- +100 +100 +100 1.0 mils 90
FPM B F H -- -- -- +100 +100 +100 2.0 mils 60 FPM HB H H 25 37 42
+100 +100 +100 2.0 mils 90 FPM B F H 22 30 37 +100 +100 +100 0.5
mils 60 FPM HB H H -- -- -- 55 65 80 0.5 mils 90 FPM B F H -- -- --
35 50 60 1.0 mils 60 FPM HB H H -- -- -- +100 +100 +100 1.0 mils 90
FPM HB F H -- -- -- +100 +100 +100 2.0 mils 60 FPM HB H H 25 33 42
+100 +100 +100 2.0 mils 90 FPM B F H 24 29 39 +100 +100 +100
__________________________________________________________________________
EXAMPLE 5
The UPEMi-vinyl ether polyester system of the above examples was
formulated with the free radical catalyst mixture, a cationic
photoinitiator UVI-6974, and with a mixture of each of the above
catalysts. The system was coated onto a polyethylene film window
and FTIR spectra was measured at 1610 cm.sup.-1 and 775 cm.sup.-1
for the uncured film. The films were then cured using an arc lamp
having a 121 milliwatts power. FTIR was remeasured at the same
wavelengths. The % conversion of the DVE-3 vinyl ether and the
maleate bonds were measured and appear below in Table 5.
TABLE 5 ______________________________________ Using UPEMi-vinyl
ether to study double bond conversion by FTIR with free radical
and/or cationic catalyst % conversion DVE3 % conversion Maleate
(1610 cm-1) (775 cm-1) UV Dose (J/cm.sup.2) 0.24 0.605 1.21 0.24
0.605 1.21 ______________________________________ 1% free radical
43.1 66.65 76.4 51.15 74.1 79.2 1.5% free radical 40.7 65.5 70.1
54.8 75.9 81 1% cationic 48.2 75.85 80 36.4 42.8 50.4 2% cationic
63.2 81 81 35.4 45.9 46 1% rad + 0.5% cat 32 63.1 71.95 54.5 70.3
75 0.5% rad + 1% cat 36.1 83.7 85.7 41.8 61.3 67.55 1% rad + 1% cat
77.5 93.4 98.9 62.6 71.1 76.3
______________________________________
EXAMPLE 5B
The sample mixes of Example 5 were drawn down on glass panels at 12
microns and cured at 54 meters/min. using a 120 w/cm arc lamp
equipped with a H bulb. The results are shown in Table 5B.
FIG. 1 and FIG. 2 illustrate a plot of % conversion verses UV dose
for the vinyl ether and maleiate double bonds produced in Examples
5 and 5B and Tables 5-and 5B.
TABLE 5B ______________________________________ Curing of the
solutions from Example 5B with an arc lamp Photoinitiator Number of
Pass Pencil Hardness ______________________________________ 1% free
radical 3 HB 1% cationic 8 <6B 2% cationic 7 <6B 1% rad 0.5%
cat 3 H 0.5% rad 1% cat 3 HB 1% rad 1% cat 2 H
______________________________________
While this invention has been described as having preferred design,
it is understood that it is capable of further modification, uses
and/or adaptations following in general the principle of the
invention and including such departures from the present disclosure
as come within known or customary practice in the art to which the
invention pertains, and as may be applied to the essential features
set forth, and fall within the scope of the invention or the limits
of the appended claims.
* * * * *